1. Field of the Invention
The present invention relates to a magneto-resistive element that senses magnetism by supplying a sense current to a magneto-resistive film.
2. Description of the Related Art
Magnetic devices, in particular, magnetic heads have made a remarkable improvement in their performance by using a giant magneto-resistive effect (GMR). The application of a spin-valve film (SV film) especially to magnetic heads, MRM (Magnetic Random Access Memories), and the like has led to a great technical progress in a magnetic device field.
The “spin-valve film” is a multilayer film including a structure in which a nonmagnetic spacer layer is interposed between two ferromagnetic layers, and a portion of the multilayer film structure where a resistance change occurs is called a spin-dependent scattering unit. Magnetization of one of the two ferromagnetic layers (called “a pinned layer”, “a magnetization fixed layer”, or the like) is fixed by an antiferromagnetic layer or the like, whereas a magnetization direction of the other ferromagnetic layer (called “a free layer”, “a magnetization free layer”, or the like) is rotatable depending on an external magnetic field. In the spin-valve film, a change of a relative angle of the magnetization directions of the pinned layer and the free layer produces a giant magneto-resistance. Here, the spacer layer magnetically separates the pinned layer and the free layer from each other to allow the magnetization directions of these layers to move independently.
Magneto-resistive effect elements using a spin valve film include a CIP (Current-In-Plane)-GMR element, a CPP (Current-Perpendicular-to-Plane)-GMR element, and a TMR (Tunneling Magneto Resistance) element. In the CIP-GMR element, a sense current is supplied in parallel to a plane of the spin valve film, while in the CPP-GMR element and the TMR element, a sense current is supplied substantially perpendicularly to the plane of the spin valve film.
In the current-perpendicular-to-plane type, a spacer layer in the TMR element is an insulation layer, and a spacer layer in a normal CPP-GMR element is a metal layer. As a developed form of the CPP-GMR element, there has also been proposed a magneto-resistive element in which a spacer layer is an oxide layer including a nano-size metal current path penetrating in a thickness direction [NOL (nano-oxide layer)]. This spacer layer has a current-confined-path (CCP) for causing metal conduction in part of the NOL (see JP-A 2002-208744 (KOKAI)).